Bump puppeteer from 20.0.0 to 21.2.0

Bumps [puppeteer](https://github.com/puppeteer/puppeteer) from 20.0.0 to 21.2.0.
- [Release notes](https://github.com/puppeteer/puppeteer/releases)
- [Changelog](https://github.com/puppeteer/puppeteer/blob/main/release-please-config.json)
- [Commits](puppeteer/puppeteer@puppeteer-v20.0.0...puppeteer-v21.2.0)

---
updated-dependencies:
- dependency-name: puppeteer
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

package.json

@@ -5,7 +5,7 @@
     "esbuild": "^0.19.2",
     "govuk-frontend": "4.7.0",
     "sass": "^1.66.1",
-    "puppeteer": "20.0.0"
+    "puppeteer": "21.2.0"
   },
   "scripts": {
     "build:css": "sass ./app/assets/stylesheets/main.scss:./app/assets/builds/main.css --no-source-map --load-path=node_modules --quiet-deps",